Mice living in heating vents will give off a powerful and unpleasant odour, especially when they fill the space with their urine and faeces. Mice sometimes build their nests in air vents, blocking the airflow. Placing poisoned bait in your ductwork might seem like a surefire way of killing any mice that have moved in, but you should avoid this approach at all costs. If you think the stench from a live mouse is bad, the stink of a decomposing mouse corpse is even worse. Decaying mice can also attract other pests and spread even worse diseases than they usually do.
It’s better to keep mice out of your vents from the start than having to try and extricate them after they’ve moved in. If you know you have a mouse infestation in your home, you should immediately ensure that your vents are sealed off and protected, so they have no chance of getting in. Remember that mice can squeeze their bodies through the narrowest of gaps. They are determined creatures; if they want to access your vents, they will do everything they can to find an entry point.
If it’s too late to think about prevention and mice are already inside your vents, getting them out isn’t easy. You’ll need to switch your central heating system off before you go looking for them. Turning the heating off will make your vents a much less attractive prospect for mice and cool your grates so you can unscrew and remove them. If you know how mice have been able to access your vents, placing traps around the entrance they’re using has a good chance of trapping them. If they have already built a nest or there are too many for you to trap, you’ll need to call a professional contractor.